[Gluster-users] High CPU/load, High latency on FSYNC

Yong Zhang hiscal at outlook.com
Sat Apr 1 00:58:57 UTC 2017


Hi, Serkan

I’m using Glusterfs as my Kubernetes storage backend, and Prometheus is running inside Kubernetes cluster. If this is not recommended I’ll consider running Prometheus outside of Kubernetes. But why performance is totally different on two nodes? Will data be written to both nodes at the same time?


From: Serkan Çoban<mailto:cobanserkan at gmail.com>
Sent: Friday, March 31, 2017 4:08 PM
To: Yong Zhang<mailto:hiscal at outlook.com>
Cc: gluster-users at gluster.org<mailto:gluster-users at gluster.org>
Subject: Re: [Gluster-users] High CPU/load, High latency on FSYNC

Prometheus uses *LOTS* of small files and do small random-io.
I do not recommend to use data volume of prometheus on glusterfs.
Why you need that?


On Fri, Mar 31, 2017 at 10:30 AM, Yong Zhang <hiscal at outlook.com<mailto:hiscal at outlook.com>> wrote:
Hi, All

I have glusterfs 3.10.0 running with two replicated nodes, but one of the node has a bad CPU performance:

Node1/Node2: 4 core, 8GB, using thin LVM for volumes

This is node1:
[cid:image005.png at 01D2AA33.B41E14D0]

And this is node2:
[cid:image006.png at 01D2AA33.B41E14D0]

Currently I have only Prometheus using glusterfs volumes, so I started profile on volume prometheus and got this:

Brick: 10.10.0.100:/glusterfsvolumes/devops/devops-prometheus/brick
-------------------------------------------------------------------
Cumulative Stats:
   Block Size:                  2b+                   4b+                   8b+
 No. of Reads:                    0                     0                     0
No. of Writes:                    1                     1                    31

   Block Size:                 16b+                  32b+                  64b+
 No. of Reads:                    0                     1                     0
No. of Writes:                   20                  4283                  3085

   Block Size:                128b+                 256b+                 512b+
 No. of Reads:                    0                     1                     0
No. of Writes:                  395                   465                   555

   Block Size:               1024b+                2048b+                4096b+
 No. of Reads:                    4                     6                    32
No. of Writes:                72453                 62462                 52882

   Block Size:               8192b+               16384b+               32768b+
 No. of Reads:                  154                   281                   484
No. of Writes:                43122                 21700                 17817

   Block Size:              65536b+              131072b+
 No. of Reads:                  993                 15290
No. of Writes:                56237                581071
 %-latency   Avg-latency   Min-Latency   Max-Latency   No. of calls         Fop
---------   -----------   -----------   -----------   ------------        ----
      0.00       0.00 us       0.00 us       0.00 us         205094      FORGET
      0.00       0.00 us       0.00 us       0.00 us         245895     RELEASE
      0.00       0.00 us       0.00 us       0.00 us          40492  RELEASEDIR
      0.00      20.50 us      19.00 us      22.00 us              2    FSYNCDIR
      0.01      99.00 us      99.00 us      99.00 us              1    GETXATTR
      0.01      68.50 us      48.00 us      89.00 us              2     OPENDIR
      0.03      84.33 us      40.00 us     164.00 us              6       FSTAT
      0.10      64.35 us      34.00 us     177.00 us             23      STATFS
      0.16      62.87 us      29.00 us     172.00 us             38        STAT
      0.17      54.76 us      22.00 us     194.00 us             46     ENTRYLK
      0.18      41.66 us      24.00 us      95.00 us             62       FLUSH
      0.22     198.44 us     138.00 us     339.00 us             16      CREATE
      0.32     101.65 us      65.00 us     184.00 us             46        OPEN
      0.35     726.43 us     350.00 us    1165.00 us              7      UNLINK
      0.52      56.22 us      25.00 us     228.00 us            136    FINODELK
      0.77     129.15 us      49.00 us    1138.00 us             87        READ
      1.57     154.70 us      59.00 us     360.00 us            148    FXATTROP
      2.44     159.13 us      41.00 us    5836.00 us            224       WRITE
      3.64     188.62 us      54.00 us     848.00 us            282      LOOKUP
     89.50   20741.70 us    9457.00 us   84733.00 us             63       FSYNC
    Duration: 362318 seconds
   Data Read: 2132763575<tel:(213)%20276-3575> bytes
Data Written: 83056358475 bytes
Interval 0 Stats:
   Block Size:                  2b+                   4b+                   8b+
 No. of Reads:                    0                     0                     0
No. of Writes:                    1                     1                    31

   Block Size:                 16b+                  32b+                  64b+
 No. of Reads:                    0                     1                     0
No. of Writes:                   20                  4283                  3085

   Block Size:                128b+                 256b+                 512b+
 No. of Reads:                    0                     1                     0
No. of Writes:                  395                   465                   555

   Block Size:               1024b+                2048b+                4096b+
 No. of Reads:                    4                     6                    32
No. of Writes:                72453                 62462                 52882

   Block Size:               8192b+               16384b+               32768b+
 No. of Reads:                  154                   281                   484
No. of Writes:                43122                 21700                 17817

   Block Size:              65536b+              131072b+
 No. of Reads:                  993                 15290
No. of Writes:                56237                581071
 %-latency   Avg-latency   Min-Latency   Max-Latency   No. of calls         Fop
---------   -----------   -----------   -----------   ------------        ----
      0.00       0.00 us       0.00 us       0.00 us         205094      FORGET
      0.00       0.00 us       0.00 us       0.00 us         245895     RELEASE
      0.00       0.00 us       0.00 us       0.00 us          40492  RELEASEDIR
      0.00      20.50 us      19.00 us      22.00 us              2    FSYNCDIR
      0.01      99.00 us      99.00 us      99.00 us              1    GETXATTR
      0.01      68.50 us      48.00 us      89.00 us              2     OPENDIR
      0.03      84.33 us      40.00 us     164.00 us              6       FSTAT
      0.10      64.35 us      34.00 us     177.00 us             23      STATFS
      0.16      62.87 us      29.00 us     172.00 us             38        STAT
      0.17      54.76 us      22.00 us     194.00 us             46     ENTRYLK
      0.18      41.66 us      24.00 us      95.00 us             62       FLUSH
      0.22     198.44 us     138.00 us     339.00 us             16      CREATE
      0.32     101.65 us      65.00 us     184.00 us             46        OPEN
      0.35     726.43 us     350.00 us    1165.00 us              7      UNLINK
      0.52      56.22 us      25.00 us     228.00 us            136    FINODELK
      0.77     129.15 us      49.00 us    1138.00 us             87        READ
      1.57     154.70 us      59.00 us     360.00 us            148    FXATTROP
      2.44     159.13 us      41.00 us    5836.00 us            224       WRITE
      3.64     188.62 us      54.00 us     848.00 us            282      LOOKUP
     89.50   20741.70 us    9457.00 us   84733.00 us             63       FSYNC
    Duration: 362318 seconds
   Data Read: 2132763575<tel:(213)%20276-3575> bytes
Data Written: 83056358475 bytes
Brick: 10.10.0.101:/glusterfsvolumes/devops/devops-prometheus/brick
-------------------------------------------------------------------
Cumulative Stats:
   Block Size:                  2b+                   4b+                   8b+
 No. of Reads:                    0                     0                     0
No. of Writes:                    1                     1                    31

   Block Size:                 16b+                  32b+                  64b+
 No. of Reads:                    0                     0                     0
No. of Writes:                   20                  4283                  3085

   Block Size:                128b+                 256b+                 512b+
 No. of Reads:                    1                     3                     2
No. of Writes:                  395                   465                   555

   Block Size:               1024b+                2048b+                4096b+
 No. of Reads:                    2                    14                    22
No. of Writes:                72453                 62462                 52882

   Block Size:               8192b+               16384b+               32768b+
 No. of Reads:                  166                   253                   502
No. of Writes:                43122                 21700                 17817

   Block Size:              65536b+              131072b+
 No. of Reads:                  893                 14392
No. of Writes:                56237                581071
 %-latency   Avg-latency   Min-Latency   Max-Latency   No. of calls         Fop
---------   -----------   -----------   -----------   ------------        ----
      0.00       0.00 us       0.00 us       0.00 us         205094      FORGET
      0.00       0.00 us       0.00 us       0.00 us         245861     RELEASE
      0.00       0.00 us       0.00 us       0.00 us          40492  RELEASEDIR
      0.01      89.00 us      89.00 us      89.00 us              1    GETXATTR
      0.02      62.00 us      53.00 us      71.00 us              2     OPENDIR
      0.02      57.00 us      51.00 us      61.00 us              3       FSTAT
      0.04     178.00 us      38.00 us     318.00 us              2    FSYNCDIR
      0.12     474.00 us     451.00 us     497.00 us              2    READDIRP
      0.18      64.00 us      28.00 us     113.00 us             23      STATFS
      0.28      48.30 us      18.00 us     184.00 us             46     ENTRYLK
      0.31      41.33 us      18.00 us      87.00 us             60       FLUSH
      0.33      66.12 us      28.00 us     246.00 us             40        STAT
      0.57     102.39 us      62.00 us     236.00 us             44        OPEN
      0.58     664.86 us     311.00 us     855.00 us              7      UNLINK
      0.86      51.37 us      22.00 us     101.00 us            134    FINODELK
      1.07     118.28 us      46.00 us     437.00 us             72        READ
      3.83     137.39 us      41.00 us    2431.00 us            222       WRITE
      4.54     250.94 us      57.00 us   15444.00 us            144    FXATTROP
      5.89    2932.56 us     134.00 us   17675.00 us             16      CREATE
      7.83     224.34 us      61.00 us   12509.00 us            278      LOOKUP
     73.50    9592.56 us    6897.00 us   36321.00 us             61       FSYNC
    Duration: 362152 seconds
   Data Read: 2005452176 bytes
Data Written: 83056358475 bytes
Interval 0 Stats:
   Block Size:                  2b+                   4b+                   8b+
 No. of Reads:                    0                     0                     0
No. of Writes:                    1                     1                    31

   Block Size:                 16b+                  32b+                  64b+
 No. of Reads:                    0                     0                     0
No. of Writes:                   20                  4283                  3085

   Block Size:                128b+                 256b+                 512b+
 No. of Reads:                    1                     3                     2
No. of Writes:                  395                   465                   555

   Block Size:               1024b+                2048b+                4096b+
 No. of Reads:                    2                    14                    22
No. of Writes:                72453                 62462                 52882

   Block Size:               8192b+               16384b+               32768b+
 No. of Reads:                  166                   253                   502
No. of Writes:                43122                 21700                 17817

   Block Size:              65536b+              131072b+
 No. of Reads:                  893                 14392
No. of Writes:                56237                581071
 %-latency   Avg-latency   Min-Latency   Max-Latency   No. of calls         Fop
---------   -----------   -----------   -----------   ------------        ----
      0.00       0.00 us       0.00 us       0.00 us         205094      FORGET
      0.00       0.00 us       0.00 us       0.00 us         245861     RELEASE
      0.00       0.00 us       0.00 us       0.00 us          40492  RELEASEDIR
      0.01      89.00 us      89.00 us      89.00 us              1    GETXATTR
      0.02      62.00 us      53.00 us      71.00 us              2     OPENDIR
      0.02      57.00 us      51.00 us      61.00 us              3       FSTAT
      0.04     178.00 us      38.00 us     318.00 us              2    FSYNCDIR
      0.12     474.00 us     451.00 us     497.00 us              2    READDIRP
      0.18      64.00 us      28.00 us     113.00 us             23      STATFS
      0.28      48.30 us      18.00 us     184.00 us             46     ENTRYLK
      0.31      41.33 us      18.00 us      87.00 us             60       FLUSH
      0.33      66.12 us      28.00 us     246.00 us             40        STAT
      0.57     102.39 us      62.00 us     236.00 us             44        OPEN
      0.58     664.86 us     311.00 us     855.00 us              7      UNLINK
      0.86      51.37 us      22.00 us     101.00 us            134    FINODELK
      1.07     118.28 us      46.00 us     437.00 us             72        READ
      3.83     137.39 us      41.00 us    2431.00 us            222       WRITE
      4.54     250.94 us      57.00 us   15444.00 us            144    FXATTROP
      5.89    2932.56 us     134.00 us   17675.00 us             16      CREATE
      7.83     224.34 us      61.00 us   12509.00 us            278      LOOKUP
     73.50    9592.56 us    6897.00 us   36321.00 us             61       FSYNC
    Duration: 362152 seconds
   Data Read: 2005452176 bytes
Data Written: 83056358475 bytes


Seems latency of FSYNC is very high. Sometimes cpu wait is also very high:

top - 15:27:39 up 4 days,  4:58,  2 users,  load average: 0.75, 0.72, 0.70
Tasks: 210 total,   1 running, 209 sleeping,   0 stopped,   0 zombie
%Cpu(s):  0.3 us,  0.2 sy,  0.0 ni, 62.9 id, 36.5 wa,  0.0 hi,  0.1 si,  0.0 st
KiB Mem :  8043984 total,   883420 free,  1788912 used,  5371652 buff/cache
KiB Swap:        0 total,        0 free,        0 used.  5819396 avail Mem

Any ideas?

Thanks.

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